Intrusive rocks of the Serra Geral Formationin eastern of Paraná Basin in the State of São Paulo: petrographic and geochemistry topics - preliminary analysis.

Abstract

The purpose of this paper is to present preliminary aspects of the petrography and chemistry of intrusive rocks (sills and dykes) from the eastern portion of the Paraná Basin in the State of São Paulo. Data from 80 samples of the region show a subaphyric and subophitic nature and have plagioclase (25-50%), augite (3-39%), pigeonite (0-10%) and magnetite (4-20%) as an essential minerals. Apatite and quartz are present as accessory minerals. The geochemical data of intrusive rocks show a basic to intermediate composition (48% < SiO2 < 56%) and a high Ti nature (TiO2 > 2%). Based on the minor and trace composition of the intrusive rocks, two different magma types were recognized, named Paranapanema and Pitanga. The spatial distribution of these magma types is not alleatory in the studied region. The intrusive rocks of Pitanga magma type are displayed in the Campinas-Paulínia region, while the Paranapanema magma type cover a large region above that one, between Rio Claro and Cajuru. Furthermore, the chemical composition of the lava flows of the Serra Geral Formation, sampled in this work, reveals a magma of Urubici type. So, the intrusive rocks of the eastern portion of the of State São Paulo are not the extension of the lava flows, or they aren’t a portions which don’t reach the surface.